Currently, there are efforts to build “electronic tongue” sensors capable of sensing chemicals in complex liquids, and vapor sensors for sensing organic vapor using polymer-coated surface acoustic wave (SAW) sensors (Grate, Chem. Rev., vol. 1000, pp. 2627-48, 2000; Rose et al, Nature, vol. 434, pp. 876-9, 2005). However, there is no sensor available with a sufficiently high sensitivity for the detection of explosives and chemical warfare agents, as well as environmental contaminants, and in general all volatile and semi-volatile molecules. The biggest challenge is the identification of a receptor with a high binding specificity to its respective target molecule against a background of various interfering agents.